Problem: Which of these numbers is composite? ${3,\ 11,\ 12,\ 19,\ 41}$
Answer: A composite number is a number that has more than two factors (including 1 and itself). 3, 11, 19, and 41 each have only two factors. The factors of 12 are 1, 2, 3, 4, 6, and 12. Thus, 12 is the composite number.